riscv64-unknown-elf-as -march=rv32ec_zicsr -mabi=ilp32e usart_and_i2c.s -o usart_and_i2c.o
#riscv64-unknown-elf-ld usart_and_i2c.o -o usart_and_i2c.elf
riscv64-unknown-elf-objdump -S usart_and_i2c.o > usart_and_i2c.lst
riscv64-unknown-elf-objcopy -O binary usart_and_i2c.o usart_and_i2c.bin
riscv64-unknown-elf-objcopy -O ihex usart_and_i2c.o usart_and_i2c.hex